The invention relates to a method and a mechanism for the continuous damping or hydration of free flowing foodstuffs and animal feed, such as grain and milled grain products, as well as the use of a damping machine.
The wetting of free flowing foodstuffs and animal feed is subject to at least two special requirements. Firstly, it is important that a fairly small quantity of wetting agent, usually water or steam, is uniformly mixed with a large quantity of dry material. The second requirement is that the wetting agent should be distributed to each particle or individual grain and cover the entire surface thereof. In some applications, water is added simply to increase the water content, although, usually, the intention is to exert, or trigger, a favourable physical or biochemical influence on subsequent processing by creating favourable process conditions. The historical background to the practice of damping grain prior to milling, as seen over the past 100 years, is most interesting. According to the German patent specification No. 77 903, for example, at the start of industrial milling the main concern was the correct dosage of water for a given cereal throughput. Since then, the so-called damping screw with a screw conveyor rotating slowly in a trough and a water metering device located in the inlet area, has proved the most successful method which, in some instances, has remained in use to this day. Such damping screws can still be found in older mills. According to the German patent specification No. 1 094 078, efforts were made, for a considerable period of time, to simultaneously introduce some thermal treatment by steam action. Numerous tests have shown that, with some types of wheat, the introduction of moisture and heat has a positive effect on subsequent processing. However, as mill output and electrical energy costs rose, the heating and subsequent cooling of large quantities was no longer viable on account of the electrical energy consumption. Surprisingly, milling practice confirmed over many decades that the uniformity of water distribution on individual grains is not of prime consideration at the time the water is added, since experience has shown that 1 to 2 days of reaction time in the so-called tempering bin completely compensates for any initial distribution deficiencies of the damping water. The water penetrates the outer layers to optimize the internal part of each grain for subsequent milling.
Up until 20 years ago, to achieve a high degree of purity of the grain, it was common practice to wash the grain in a proper wash process, which served to remove stones at the same time. The high water consumption rate of 1 to 2 liters/kg of grain created enormous waste water problems which led, ultimately, to the development of the dry destoner. Thus, any heat treatment was frustrated by the high cost of electrical energy and washing by the cost of the wash water. Complete dry cleaning and damping in accordance with the applicant's German patent specification No. 25 03 383 has become the most widespread method in the past ten years. Damping water distribution is all the more homogenous, the more intensively the grain is mixed with the water and worked during damping. At the same time this method has the disadvantage of causing more grain damage and more abrasion. A water addition system should dampen the grain without causing abrasion. The water addition system should be designed so that the water acts on the grain to optimize it for subsequent milling. As far as damping is concerned, this has turned into a conflict of objectives.